Web application services (Web AS) are commercially available from a number of vendors, such as: NetWeaver Application Server, available from SAP AG, Walldorf, Germany; Apache HTTP Server, version 2.2.0, available from Apache HTTP Server Project, Apache Software Foundation; and Internet Information Services (IIS) 6.0, available from Microsoft Corporation, Redmond, Wash.
Web AS generally are platform-independent, and highly scalable using sophisticated caching, dispatching, and messaging techniques in a distributed computing environment. Web AS may employ a number, or cluster, of application server (AS) instances, each of which may support a number of work processes for receiving and responding to service requests from clients. The cluster of AS instances may be distributed over one or more computing platforms, and typically communicate with each other via a messaging service.